Forwarded message:
From giurfa Fri Jan 21 16:41:38 1994
Subject: Re: Trying again
To: [log in to unmask] (Peter Kevan)
Date: Fri, 21 Jan 1994 16:41:38 +0100 (MET)
From: Martin Giurfa <castor!giurfa>
In-Reply-To: <[log in to unmask]> from "Peter Kevan" at
 Jan 20, 94 05:25:44 pm
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> How much nectar is in a crop-load? I seem to remember reading that its
> about 1 milliliter, can that be? Cheers, Peter Kevan ([log in to unmask])
>
        For honeybees, the maximal crop load is 60 microliter. This can
vary from forager to forager, of course but this is the normal value for
a full croap load. OF COURSE, THE MAIN POINT IS THAT HONEYBEES DO NOT
ALWAYS FILL THEIR CROP WHEN FORAGING. Also for profitable food sources
foragers can come back to the hive with a half croap (30 microliter).
THE TRICK THERE IS THAT BY REDUCING THEIR CROAP LOADS WHEN EXPLOITING
A PROFITABLE FOOD SOURCE, BEES REDUCE THEIR FORAGING TIME (TIME OUTSIDE
THE HIVE) AND INCREASE IN THAT WAY THE EFFICACITY OF THE INFORMATION
CHANNEL BETWWEN THE HIVE AND THE FOOD SOURCE.
        This is valid for a social insect like the honeybee where informa-
tion exchange plays a fundamental role in foaraging strategies but it is
not necessarily valid for bumblebees and (obviously) solitary bees.
        In any case, for quantification of the croap load in honeybees
and quantification of the strategies that vary accordingly, I would suggest:
 
Nunez JA (1970) The relationship between sugar flow and foraging and recrui-
                ting behaviour of honeybees. Anim Behav 18: 527-538
Nunez JA (1982) Honeybee foraging strategies at a food source in relation
                to its distance from the hive and the rate of sugar flow.
                J Apic Res 21:139-150
 
Also: Varju D & Nunez JA (1991): What do foraging honeybees optimize? J Comp
                Physiol A 169: 729-736.
 
 
        The ultimate argument to explain why honeybees do not fill their
croap was also discussed by Paul Schmid-Hempel who proposed other explana-
tions in terms of individual efficiency, BUT WHAT IS SURE IS THAT HONEYBEES
DO NOT NECESSARILY RETURN TO THE HIVE WITH A FULL CROAP WHEN EXPLOITING A
PROFITABLE FOOD SOURCE. THE SAME IS OF COURSE VALID FOR A NON PROFITABLE
FOOD SOURCE.
 
        Cheers,
 
 
 
 
                        Martin Giurfa
                        Institut fuer Neurobiologie
                        Freie Universitaet Berlin
                        Koenigign Luise Str. 28/30
                        14195 BERLIN - GERMANY
 
                        [log in to unmask]